An AMLCD device has the advantages of portability, low power consumption, and low radiation, and has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the AMLCD device is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
Referring to FIG. 4 and FIG. 5, a typical AMLCD panel 10 of an AMLCD device includes a color filter (CF) substrate 100, a thin film transistor (TFT) substrate 300, and a liquid crystal layer 200 sandwiched between the two substrates 100, 300. The AMLCD panel 10 is a twisted nematic (TN) LCD panel, and works in a so-called “normally white” mode.
The CF substrate 100 includes a first glass substrate 101, a first polarizer 106, a black matrix 105, a color filter unit film 103, a common electrode layer 104, and a first alignment layer 102. The first polarizer 106 is formed on an outside surface of the first glass substrate 101. The black matrix 105 and the color filter unit film 103 are formed on an internal surface of the first glass substrate 101 nearest to the liquid crystal layer 200. The color filter unit film 103 includes a plurality of red color filter units (R), a plurality of green color filter units (G), and a plurality of blue color filter units (B). The red color filter units (R), the green color filter units (G), and the blue color filter units (B) are positioned on the first glass substrate 101 in a predetermined arrangement, and are separated from each other by the black matrix 105. The common electrode layer 104 is formed on the black matrix 105 and the color filter unit film 103. The first alignment layer 102 is formed on a surface of the common electrode layer 104 nearest to the liquid crystal layer 200. The first alignment layer 102 includes a plurality of first grooves (not shown) that extend along a ten o'clock direction of the AMLCD panel 10 when the AMLCD panel 10 is viewed from above (corresponding to the view of FIG. 4).
The TFT substrate 300 includes a second glass substrate 301, a second polarizer 305, a second alignment layer 303, a plurality of gate lines 306 that are parallel to each other and that each extend along a first direction, a plurality of common lines 316 that are arranged parallel to and alternate with the gate lines 306, a plurality of data lines 308 that are parallel to each other and that each extend along a second direction orthogonal to the first direction, a plurality of thin film transistors (TFTs) 302 each of which is provided in the vicinity of a respective point of intersection of one of the gate lines 306 and one of the data lines 308, a plurality of pixel electrodes 304, a plurality of first shield metal lines 320 electrically connected to the common lines 316, a plurality of second shield metal lines 321 electrically connected to the common lines 316, and a plurality of through holes 331.
The second polarizer 305 is formed on an outside surface of the second glass substrate 301. The second alignment layer 303 is positioned adjacent to the liquid crystal layer 200. The second alignment layer 303 includes a plurality of second grooves (not shown) that extend along a one o'clock direction of the AMLCD panel 10 when the AMLCD panel 10 is viewed from above.
The gate lines 306, the common lines 316, the data lines 308, the TFTs 302, the pixel electrodes 304, the first shield metal lines 320, and the second shield metal lines 321 are formed at an internal surface of the second glass substrate 301 nearest to the liquid crystal layer 200. The gate lines 306 cross the data lines 308, thereby define a plurality of pixel regions (not labeled).
In each pixel region, the TFT substrate 300 includes a pair of data lines 308, a pair of gate lines 306, a common line 316, a TFT 302 which functions as a switching element, a pixel electrode 304, a pair of first and second shield metal lines 320, 321, and a through hole 331. The TFT 302 includes a gate electrode 302b connected to one of the pair of gate lines 306, a source electrode 302a connected to one of the pair of data lines 308, and a drain electrode 302c connected to the pixel electrode 304 via the through hole 331. The pair of shield metal lines 320, 321 are adjacent and parallel to the pair of data lines 308 respectively. That is, the pair of shield metal lines 320, 321 are located at two opposite sides of the pixel electrode 304 respectively. The second shield metal line 321 partly overlaps the pixel electrode 304 to form a first capacitor 311. The first shield metal line 320 partly overlaps the pixel electrode 304 to form a second capacitor 312. The common line 316 includes an ear part (not labeled), which partly overlaps the pixel electrode 304 to form a third capacitor 310.
FIG. 6 is a voltage-transmittance diagram which represents a relationship between light transmittance of a pixel unit of the AMLCD 10 and a gradation voltage applied to the pixel unit. The first grooves of the first alignment layer 102 extend along the ten o'clock direction and the second grooves of the second alignment layer 303 extend along the one o'clock direction, thus an optical viewing angle of the AMLCD panel 10 extends along a three o'clock direction. When an electric field is applied to the AMLCD panel 10 in order to provide a black image viewed on a display screen of the AMLCD panel 10, liquid crystal molecules 211 of the liquid crystal layer 200 should align perpendicular to the two substrates 100, 300. However, when an electric field generated by voltages respectively provided by the pixel electrode 304, the data line 308, the common electrode 104, the first shield metal line 320, and the second shield metal line 321 is applied to the liquid crystal molecules 211 between the two substrates 100, 300, a light-leakage region (not labeled) may appear near the black matrix 105. The light-leakage region includes a first light-leakage area 210, a second light-leakage area 212, and a third light-leakage area 214. Liquid crystal molecules 211 in the first, second and third light-leakage areas 210, 212, 214 are arranged as shown.
The first light-leakage area 210 and the second light-leakage area 212 are positioned below the black matrix 105. The liquid crystal molecules 211 in the first and second light-leakage areas 210, 212 are aligned parallel to the two substrates 100, 300. The third light-leakage area 214 is adjacent to the second light-leakage area 212, and is not covered by the black matrix 105. The liquid crystal molecules 211 in the third light-leakage area 214 are also aligned parallel to the two substrates 100, 300. Thus light penetrates the AMLCD panel 10 in the light-leakage region, and the arrayed combination of the pixel colors provides an impaired image viewed on the AMLCD panel 10. The light penetrating the first and the second light-leakage areas 210, 212 may be blocked by the black matrix 105 above the first and the second light-leakage areas 210, 212.
However, in order to block the light penetrating the third light-leakage area 214, an area (or a width) of the black matrix 105 would need to be increased. If the black matrix 105 is configured thus, an aperture ratio of the AMLCD 10 is correspondingly reduced.
What is needed, therefore, is an AMLCD panel that can overcome the above-described deficiencies.